1. Field of the Invention
The invention consists of a tool perfected and particularly suited to the pressure wire drawing of wire rods and wires, with a separate and detachable pressure die and drawing die.
2. Description of the Related Art
The operation of wire drawing, well known in the technical literature, consists of reducing the diameter of wire rods or wires by means of plastic deformation effected by a tool of appropriate shape known as a wire drawing die.
Wire is passed through the above mentioned tool by means of electrically driven bobbins so the diameter of the wire is reduced during this forced passage.
One critical aspect of the whole operation is that of lubrication of the wire, which must be optimum in order to prevent the tool from seizing. The length of the entrance cone of the wire drawing die, which acts as a pump for the lubricant due to the continuous movement caused by the sliding of the lubricant in the tool, improves the attachment of the lubricant to the wire, but there remain problems of sealing inside the wire drawing die itself.
One well-known solution in the technical literature is that of wire drawing dies consisting of a single wire drawing nib made of tungsten carbide encased by shrink-fitting in a case that is carefully shaped on the inside, altogether this constitutes one single piece which is filled directly on machines designed for wire drawing operations.
A more recent tool has a case of steel, in two parts, that can be taken apart, where the upper part is shaped on the inside to house a die known as a pressure die made of tungsten carbide, while the lower part is designed to contain a wire drawing nib, again made of tungsten carbide, designed to perform the plastic deformation or the wire rod or wire.
Although these devices meet the technical requirements described above, they nevertheless have the following disadvantages.
Once the tool consisting of a single piece is worn it must be completely replaced with an increase in total costs, since because of its components, the worn tool becomes a special waste requiring adequate disposal.
Furthermore, and again for reasons of cost, the dimensions of the tungsten carbide nib, which in this case cannot be recovered in any way, are reduced to the indispensable minimum with consequent negative results for lubrication. The quality of the finished product and the speed of production is thereby lowered.
Tools consisting of more than one part that can be assembled and taken apart present the inconvenience of the possibility of leakage of the lubricant between the pressure die and the drawing nib as well as that of the case yielding due to the high working pressures.
In this case too, costs are markedly increased because of both the mechanical breakages described above and the maintenance necessary to dismantle and replace damaged parts.
Production speed in this case too, may not be such as to exploit the maximum potential speed of wire drawing machines due to problems connected with lubrication caused by the above described leakages.
The purpose of this invention is to resolve these inconveniences inherent in the prior technology.